The primary objective of this research is to contribute to the more effective use of nonhuman primates in any experimental program in which it is necessary or desirable to know blood types of the animals involved. To this end we have developed typing serums detecting 7 factors. Seven additional antiserums are being tested for specificity. We are continuing to study the ability of certain blood factors to induce mild or severe transfusion reactions and the deviations from normal physiological functions involved in these reactions. Other continuing studies include induction of tolerance to red cells during fetal life, spontaneous or induced erythroblastosis in monkeys, relationship of certain blood factors to a metabolic disease in Celebes apes, and autoimmune hemolytic anemias.